Support for bending test of flexible substrates

ABSTRACT

A support for facilitating the bending test of flexible substrates is disclosed. The support includes a plastic or adhesive plastic applied on the substrate to keep the shards together after breakage, thereby eliminating the process of collecting the shards and fitting them back together for failure analysis.

FIELD OF THE INVENTION

[0001] The present invention relates generally to thin flexible substrates such as those used to fabricate flexible devices. More particularly, the invention relates to the stress (bending) testing of thin glass substrates.

BACKGROUND OF THE INVENTION

[0002] To access the flexibility of thin substrates, bending tests have to be performed. During these tests, the substrate is subjected to bending until it breaks. The shards have to be reconstructed for the analysis to determine the breaking behavior.

[0003] The shards are not held together but are scattered after the breakage and have to be collected and fitted back together. This process of reconstruction is time-consuming. Furthermore, it is not always possible to fit all the shards back to their original positions as the shards are small and numerous, and scatter randomly in many different directions.

[0004] As evidenced from the above discussion, it is desirable to facilitate the reconstruction process by providing a means to keep the shards together after breakage.

SUMMARY OF THE INVENTION

[0005] The invention relates generally to thin flexible substrates, such as those used in microelectronics, optoelectronics and display devices. In particular, the invention facilitates the stress testing of flexible substrates like thin glass substrates. The present invention can also be used to facilitate stress testing of non-flexible substrates like silicon chips, chips of compound semiconductors or wafers as well as glass.

[0006] In accordance with the invention, a support is provided to keep the shards of the substrate together after breakage. In one embodiment, the support comprises a plastic layer attached to one side of a substrate. Alternatively, the plastic layer can be applied to both sides of the substrate. The plastic layer can be laminated on the substrate with an adhesive. Using plastic layer which includes an adhesive or comprises adhesive properties can also be used. Such plastic layers are referred to as, for example, adhesive plastic layers. Alternatively, the plastic layer is deposited using deposition techniques such as spin-coating or spraying. Subsequently, the substrate with the support undergoes a bending test until it shows a failure.

[0007] The shards are kept together by the plastic layer after breakage, and it is no longer necessary to collect the small shards and fit them back together. Hence, a more precise and efficient failure analysis of the flexible substrate can be done.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 shows an embodiment of the invention.

[0009]FIG. 2 shows the breaking test process

PREFERRED EMBODIMENTS OF THE INVENTION

[0010]FIG. 1 shows one embodiment of the invention for facilitating stress testing of a substrate. A plastic layer 110 is attached to at least one side of a substrate 120. The substrate, for example, comprises glass. Other types of substrates, such as those formed from brittle or breakable materials or subjected to bending test, can also be used. The substrate is subjected to a bending or stress test, as shown in FIG. 2, resulting in fractures 230. The shard or shards 240 are held in place by the plastic layer after breakage.

[0011] In one embodiment, the plastic layer is attached on one side of the substrate. For substrates prepared with device layers, structures, or components on a top surface, the plastic layer preferably attached on the bottom surface of the substrate. Providing plastic layers on both surfaces can also be useful. In one embodiment, the plastic layer is attached to the surface of the substrate with an adhesive. Various types of adhesives, such as epoxy, can be used. Adhesive plastic layers processed with an adhesive or have adhesive properties can also be used. Other types of plastic layers which can be formed on and adhere to the substrate is also useful.

[0012] The plastic layer should have good adhesion to the substrate, a low Young's modulus and should not change the mechanical properties of tensile strength and bending modulus of the flexible substrate.

[0013] In one embodiment of the invention, the plastic layer is attached to the substrate by a laminating technique. Alternatively, the plastic layer is formed on the substrate using deposition techniques, such as spraying or spin-coating. Typically, the plastic layer is cross-linked after deposition. Other techniques for forming or providing the plastic sheet on the substrate are also useful. Subsequently, the substrate undergoes a bending or breaking test until it shows a failure. The fracture strain can easily be calculated from the given thickness, tensile strength and bending modulus of the substrate.

[0014] In a preferred embodiment of the invention, an adhesive plastic layer, for example the “ELEP HOLDER” wafer protection and holding tape from Nitto Denko, is deposited on one side of a thin glass substrate. The thin glass substrate, is about 50 μm thick. Another example of plastic layer that can be deposited on the substrate is the thermal release tape “REVALPHA” from Nitto Denko. In another embodiment, a laminating pouch film that, for example, is about 125 μm thick is applied onto the substrate by applying pressure and heat.

[0015] The glass substrate undergoes a bending test, during which it is bent until it breaks. The glass shards are held in place on the plastic sheet and can easily be identified.

[0016] While the invention has been particularly shown and described with reference to various embodiments, it will be recognized by those skilled in the art that modifications and changes may be made to the present invention without departing from the spirit and scope thereof. The scope of the invention should therefore be determined not with reference to the above description but with reference to the appended claims along with their full scope of equivalents. 

What is claimed is:
 1. An apparatus suitable for facilitating stress testing of substrates, the apparatus comprising a plastic layer on at least one major surface of the substrate to keep the shards together after breakage from the test.
 2. The apparatus of claim 1 wherein the substrate comprises a flexible substrate.
 3. The apparatus of claim 1 wherein the substrate comprises a non-flexible substrate.
 4. The apparatus according to claims 1, 2 or 3 wherein the plastic layer is on a first side of the substrate.
 5. The apparatus of claims 1, 2 or 3 wherein the plastic layer is applied to first and second major surfaces of the substrate.
 6. The apparatus of claim 4 wherein the plastic layer comprises a material that has good adhesion to the substrate.
 7. The apparatus of claim 6 wherein the plastic layer comprises a material with a low Young's modulus to reduces or minimizes affecting the breaking behavior of the substrate.
 8. The apparatus of claim 4 wherein the plastic layer is attached to the surfaces of the substrate with an adhesive.
 9. The apparatus of claim 8 wherein the adhesive comprises epoxy.
 10. The apparatus of claim 9 wherein the plastic layer comprises a material with a low Young's modulus to reduces or minimizes affecting the breaking behavior of the substrate.
 11. The apparatus of claim 5 wherein the plastic layer comprises a material that has good adhesion to the substrate.
 12. The apparatus of claim 11 wherein the plastic layer comprises a material with a low Young's modulus that reduces or minimizes affecting the breaking behavior of the substrate.
 13. The apparatus of claim 5 wherein the plastic layer is attached to the surface of the substrate with an adhesive.
 14. The apparatus of claim 13 wherein the adhesive comprises epoxy.
 15. A method for forming an apparatus including an apparatus to facilitate stress testing comprising: providing a substrate; and applying a plastic layer on the substrate.
 16. The method of claim 15 wherein the substrate comprises a flexible substrate.
 17. The method of claim 15 wherein the substrate comprises a non-flexible substrate.
 18. The method of claims 15, 16 or 17 wherein applying the plastic layer comprises attaching the plastic layer with an adhesive.
 19. The method of claim 18 wherein the adhesive comprises epoxy.
 20. The method of claim 19 wherein the plastic layer comprises a material with a low Young's modulus that reduces or minimizes affecting the breaking behavior of the substrate.
 21. The method of claims 15, 16 or 17 wherein the plastic layer comprises a material that has good adhesion to the substrate.
 22. The method of claim 21 wherein the plastic layer comprises a material with a low Young's modulus that reduces or minimizes affecting the breaking behavior of the substrate.
 23. The method of claim 22 wherein applying adhesive plastic on the substrate comprises application by a laminating technique.
 24. The method of claim 22 wherein applying adhesive plastic on the substrate comprises application by deposition.
 25. The method of claim 24 wherein application by deposition comprises spraying.
 26. The method of claim 25 further comprises cross-linking the plastic layer after deposition.
 27. The method of claim 24 wherein application by deposition comprises spin-coating.
 28. The method of claim 27 further comprises cross-linking the plastic layer after deposition. 